What drove Anders Breivik to unspeakable depths of mass murder? His lawyer says he is insane. He says he killed to halt the "Islamisation of Europe".

He also claimed to have links to the far right in the UK, through contactswith the English Defence League. That was enough to provoke David Cameron into demanding from the security services a review of the far right in Britain.

Hugh Muir takes a snapshot of the far right, with the help of Matthew Goodwin the author of New British Fascism: Rise of the British National Party; Matthew Taylor, who has written extensively for the Guardian on the far right; and Dan Hodges, who works with the anti fascist organisation Searchlight.

We'll consider those who seek gains through the political system, those who rely on intimidation and violence, and we'll also visit the communities they see as ripe for conflict and exploitation.

Hugh visits Tower Hamlets in east London to assess the mood ahead of the EDL march, and Martin Wainwright visits Stoke-on-Trent to find out if the BNP can still count on support there.